......or are you simply referring to standard usage of the DX90's microSD slot with a 128gb microSD card?

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"Non-moving-hard-drive storage" meaning not a mechanical drive, at least in technical terms that should be what he means.

Also interested how this ends up turning out, I currently have a "limited edition" Pono Player reserved, I am however debating on keeping it or dropping my kickstarter backing and getting the DX90 or a FiiO X5, which ever device I get will be replacing my ZuneHD.

Ayre are well-respected, but they're an unknown quantity in the DAP world (the same can be said for Calyx, incidentally), so it'll be interesting to see how the PONO SQ compares to the likes of iBasso, Fiio, etc.

If I had a gun pointing at me, and I had to guess at which of the 3 DAPs you mention probably has the best SQ (and I'm only talking about sound quality in this instance), I would place my betting chips on the DX90, but whichever of them turns out to have the best SQ, the other 2 will undoubtedly be very close indeed.

Time will tell, just wish there was more of a hard release date set for the DX90, I sent them an e-mail via their form on the iBasso website with that question, hopefully I will get some form of an answer.

or are you simply referring to standard usage of the DX90's microSD slot with a 128gb microSD card?

As was discussed earlier, the USB OTG function drains battery power, so it's not really viable for frequent use. So that basically leaves only the single MicroSD, which, in terms of market availability, maxes-out at 128gb (and I don't anticipate seeing 256 for at least 2 years, given how rediculously long it has taken for 128gb MicroSD cards to arrive). That means around 100 albums of 24/96 material, which is workable, but not exactly great. The majority of my music is currently 16/44.1, but that will gradually shift in favour of 24/96, as I buy more and more Hi-Res. It looks like most people will end up playing Redbook on the DX90, with only occasional forays into Hi-Res, owing to the limited capacity available. 24/96 can, of course, be down-converted to 24/48, and it is the mastering that is the most critical aspect affecting SQ, but still... I would only tend to reach for the down-conversion software with 24/192 - given sufficient storage options, I'd just as soon leave the 24/96 alone and play it without tampering with it. When you look at the formidable capabilities of the various ES9018 series DAC chips, it does seem crazy to not feed them at least medium-Hi-Res files if at all possible.

I've had several private conversations, recently, (not just on Head-fi, but also by phone), where the DX90s storage capabilities have been a topic of debate - many of us are hesitant to buy a DAP with no onboard memory but only one card slot. But I guess that hasn't stopped the unexpandable 128gb NW-ZX1 selling quite well, so <shrugs shoulders>

Personally, I feel the DX90 falls very short in terms of storage options, which is undoubtedly its Achilles' heel. It was a serious error to shoehorn the DX90 spec into the DX50 chassis, at the expense of no extra card slot, no balanced HO/LO (which would have been very easy to implement, given the actual DX90 amplification topology), and no extended-capacity battery. Just deepening the DX50 chassis with, say, a 4 or 5mm deeper rear plate would have allowed all of these things to happen, and without having to re-engineer the rest of the DX50 chassis/casework.

...but, for all that, is it still worth $419 for a dual-ES9018K2M with nice amp stage? Well, yes, I can't deny that it is good value. But it could have been spectacular value with these few simple changes. I really can't understand why iBasso were so doggedly determined to withhold features, just in order to forcibly squeeze it into it's older brother's chassis. Cost-saving is certainly a worthwhile endeavour, but just deepening the rear panel surely wouldn't have been that much of a bitch to achieve, and maybe drilling an extra hole for a balanced output jack of some description.

Perhaps they are betting on the price-point making this dual-DAC DAP sell like hotcakes in spite of the storage limitations, and they'll probably be proved right. For some of us, though, the search for the perfect DAP continues. ALL the current frontrunners (Calyx-M, DX90, X5, etc.) have shortcomings, and these shortcomings are utterly unnecessary, yet there they remain .

One day soon, one of these DAP-makers (and it may be Fiio, given James' obvious eagerness to please) will wake up to the fact that a bit more market-research, in terms of what customers desire, and in terms of what shortcomings their competitors' products have, could land them the biggest non-Apple payday in DAP history.

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you have said well with a very detailed explanation. but as you know, dx100 is now in its older days, just before retirement : ) so the above specs you listed would probably be on the successor of ibasso's new 'reference dap', say dx 200, or dx 120 as the astell & kern way? : )

and i am quite positive that dx 90 will be very close to dx 100 in sonic performance.

or are you simply referring to standard usage of the DX90's microSD slot with a 128gb microSD card?

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As was discussed earlier, the USB OTG function drains battery power, so it's not really viable for frequent use. So that basically leaves only the single MicroSD, which, in terms of market availability, maxes-out at 128gb

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Personally, I feel the DX90 falls very short in terms of storage options, which is undoubtedly its Achilles' heel. It was a serious error to shoehorn the DX90 spec into the DX50 chassis, at the expense of no extra card slot, no balanced HO/LO (which would have been very easy to implement, given the actual DX90 amplification topology), and no extended-capacity battery. Just deepening the DX50 chassis with, say, a 4 or 5mm deeper rear plate would have allowed all of these things to happen, and without having to re-engineer the rest of the DX50 chassis/casework.

Yes, I did mean just the regular SD card slot.

I agree with you that an OTG with the battery cover removed, etc. etc is an absolutely ridiculous solution for what is purportedly a portable solution - especially given (as I feel) that the level-matched differences between various DAPs is very small. For non-critical listening - which on-the-go sessions are - that incremental (if at all) benefit is absolutely not worth the hassle of dealing with lower battery life, a clunky UI, etc. etc.

For music on the go, ergonomics and an intuitive interface are at the top of my purchasing priorities, after ability to get a clean line-out signal. The iDevices kick ass in the former, and while I do get a LO (I have a CLAS -R and recently got a Centrance M8 as well), the solution is too bulky to carry around daily - those are my travel rigs (for flights, business travel, etc), not my day-to-day carries.

And spot on as well that iBasso dropped the pooch by going with a single-card slot. Currently, I am now torn between this and the X5. I dont like FiiO's ergonomics - not even close - to the extent that I am willing to settle for the smaller capacity of the DX90 to avoid it (or maybe not even bother with it, and stick to the DX50).

If they had put in 2 slots, ala the X5, it would have been a no-brainer - I'd have jumped on one asap. However, if Apple comes out with a 128GB iPod Touch soon, I am not going to get either the X5 or the DX90.

SQ guys, the single slot does make much of an issue, 128GB is already around. You get 2 and just swap. Can't imagine choosing the lesser SQ DAP because it has 2 slots over one. Priorities easily misplaced nowadays.

Look how beef up the DX90 is in the same package and still at bargain price. If all you can see is the single uSD slot, good luck to you.